_printf

A custom implementation of the standard C library printf function. This project demonstrates understanding of variadic functions, format specifiers, and low-level I/O operations in C.

Features

Supported Format Specifiers

Specifier	Description
c	Single character
s	String (prints "(null)" for NULL)
d, i	Signed decimal integer
u	Unsigned decimal integer
b	Binary representation
o	Octal representation
x	Lowercase hexadecimal
X	Uppercase hexadecimal
%%	Percent sign

Usage

#include "main.h"

int main(void)
{
    _printf("Character: %c\n", 'A');
    _printf("String: %s\n", "Hello, World!");
    _printf("Integer: %d\n", 42);
    _printf("Unsigned: %u\n", 255);
    _printf("Binary: %b\n", 10);
    _printf("Octal: %o\n", 64);
    _printf("Hex lowercase: %x\n", 255);
    _printf("Hex uppercase: %X\n", 255);
    _printf("Percent: %%\n");

    return (0);
}

Return Value

Returns the number of characters printed (excluding the null byte used to end output to strings).

File Structure

.
├── _printf.c          # Main printf function implementation
├── _putchar.c         # Character output function
├── _strlen.c          # String length calculation
├── get_specifier.c    # Format specifier handler
├── print_binary.c     # Binary format printing
├── print_char.c       # Character format printing
├── print_hex.c        # Lowercase hexadecimal printing
├── print_HEXA.c       # Uppercase hexadecimal printing
├── print_int.c        # Integer format printing
├── print_octal.c      # Octal format printing
├── print_string.c     # String format printing
├── print_unsigned.c   # Unsigned integer printing
├── main.h             # Header file with prototypes and definitions
└── README.md          # This file

Compilation

gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o _printf

Function Prototypes

int _printf(const char *format, ...);
int (*get_specifier(char s))(va_list);
int print_char(va_list args);
int print_string(va_list args);
int print_int(va_list args);
int print_binary(va_list args);
int print_unsigned(va_list args);
int print_octal(va_list args);
int print_hex(va_list args);
int print_HEX(va_list args);
int _putchar(char c);
int _strlen(char *s);

Implementation Details

• Uses va_list for handling variable arguments
• Employs function pointers for format specifier handling
• Uses write() system call for low-level character output
• No external dependencies beyond standard C libraries